BACKGROUND OF THE INVENTION Vehicle alternators are used to generate electrical power to charge the vehicle's battery while the engine is running. When suitably connected, they may also be used to supply electric power to various tools and accessories.

U. S. patent no. 5,436,509, which is incorporated herein by reference, describes a vehicle alternator having dual stator coils and accompanying passive control circuitry. The output of the alternator may be disconnected from the battery, so that the alternator functions as a generator and supplies DC power, of variable voltage, to welding cables or to power welding apparatus.

SUMMARY OF THE INVENTION<BR> <BR> <BR> <BR> It is an object of some aspects of the present invention to provide an improved vehicle alternator and power supply for electrical apparatus.

In preferred embodiments of the present invention, an alternator comprises one or more, preferably two, rotors and two or more stators, preferably comprising four or more stator coils, wound on two or more cores.

The rotors, which may be configured in parallel or in series, are driven to rotate by an engine, preferably the engine of a vehicle, causing a current to flow in the stators. When the alternator is in a charging configuration, the current in a first one or the stators is rectified, switched and regulated so as to charge a battery in the vehicle. Alternatively, the alternator may be disconnected from the vehicle battery, and the current in the first stator is rectified, switched and regulated to provide DC output power at a desired voltage and current, for example, to use in welding. The current in a second one of the stators is rectified, switched and regulated so as to provide a high-voltage DC output, preferably 220 VDC or, alternatively, 110 VDC or substantially any other desired voltage level.

In some preferred embodiments of the present invention, active control circuitry detects the voltage and current generated by the alternator, and varies an input current to the rotors in order to regulate the high-voltage output. The active control circuitry, which is preferably isolated from the vehicle ground (and hence from a user of the high-voltage output), enables the output to be maintained at a desired voltage level substantially irrespective of load and substantially cuts off the output if a ground fault, short circuit or overload is detected.

There is therefore provided, in accordance with a preferred embodiment oi the present invention, electric power generation apparatus for use in conjunction with a <BR> <BR> <BR> source of rotary power having a battery associated therewith, including: one or more rotors, which are driven to rotate by the source of rotary power; one or more stators, including at least a first and a second stator coil, coupled inductively to the one or more rotors, so as to generate electrical currents responsive to the rotation thereof; a first rectifier, coupled to receive and rectify the electrical current generated by the first stator coil, producing a DC output suitable for charging the battery; and a second rectifier, coupled to receive and rectify the electrical current generated by the second stator coil, producing a high-voltage DC output suitable for operating auxiliary electrical equipment coupled thereto.

Preferably, the high-voltage DC output is in a voltage range between 100 and 400 VDC, and the second rectifier provides at least 6 kW of high-voltage DC output power.

In a preferred embodiment, the one or more rotors include first and second rotors connected in parallel or, alternatively, connected in series.

In a further preferred embodiment, the one or more stators include first and second stators, each including respective first and second stator coils, wherein the respective first coils of the first and second stators are preferably arranged to provide a six-phase output, <BR> <BR> <BR> and wherein the first rectifier includes a six-phase rectifier.

Preferably, the second stator coil has a center tap which is grounded.

Preferably, the apparatus includes active control circuitry, which samples one or more of the DC outputs and varies a current input to the one or more rotors responsive thereto. Preferably, the control circuitry is coupled to the high-voltage DC output, and the control circuitry and d the second stator coil are electrically isolated from the first stator coil and from the battery.

Further preferably, the circuitry includes a controller which receives a sampled input responsive to the high-voltage DC output and generates a pulse-width modulated output to control the current input to the rotors. Preferably, the circuitry includes a gate coupled to open and close a current path through the rotors responsive to the pulse-width modulated output of the controller. Preferably, the controller modulates the pulse width responsive to a change in the voltage of the high-voltage DC output and, alternatively or additionally, decreases the current input to the rotors responsive to an excessive voltage in one or more of the stator coils.

In a preferred embodiment, the DC output of the first rectifier is decoupled from the battery and provides a high-current auxiliary electrical output, which is preferably used in welding, most preferably at a regulated voltage that is variable between about 40 and 65 VDC. in another preferred embodiment, the apparatus includes a supplementary power supply, coupled to receive power from one of the stator coils and to provide a supplementary power output, preferably a DC output to charge the battery while the first rectifier is decoupled therefrom.

In a preferred embodiment, a voltage of one or more of the DC outputs is varied by changing a resistor value in an input circuit of the controller.

There is further provided, in accordance with a preferred embodiment of the present invention, a method for generating electric power in conjunction with a source of rotary power having a battery associated therewith, including: coupling one or more rotors to the source of rotary power to be rotationally driven thereby; inductively coupling at least first and second stator coils to the one or more rotors, so as to generate electrical currents responsive to the rotation thereof; rectifying the electrical current generated by the first stator coil, to produce a DC output suitable for charging the battery; and rectifying the electrical current generated by the second stator coil, to produce a high-voltage DC output suitable for operating auxiliary electrical equipment coupled thereto.

Preferably, the high-voltage DC output is in a voltage range between 100 and 400 VDC.

In a preferred embodiment, coupling the first and second stator coils includes commonly winding respective first and second coils on each of first and second stators.

Preferably, the method includes sampling the high- voltage DC output and actively controlling a current input to the first and second rotors responsive thereto.

In a preferred embodiment, controlling the current input includes generating a pulse-width modulated signal to control the current input responsive to the sampled output. Preferably, controlling the current input includes modulating the pulse width responsive to a change in the voltage or the DC output. Alternatively or additionally, controlling the current input includes modulating the pulse width to decrease the current input to the rotors responsive to an excessive current flowing in one or more of the stators.

The present invention will be more fully understood from the following detailed description of the preferred embodiments thereof, taken together with the drawings in which: BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic block diagram showing vehicle alternator apparatus, including an alternator and associated control circuitry, in accordance with a preferred embodiment of the present invention; Fig. 2A is a schematic circuit diagram showing details of the alternator of Fig. 1, in accordance with a preferred embodiment of the present invention; and Figs. 2B, 2C and 2D are schematic circuit diagrams showing details of the control circuitry of Fig. 1, in accordance with a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Reference is now made to Fig. 1, which is a schematic block diagram showing alternator apparatus 20, including an alternator 22 and control circuitry 26 associated therewith, in accordance with a preferred embodiment of the present invention. Control circuitry 26 includes a monitor isometer 28, regulator control and automatic fusing circuits 30, and a lamp driver control circuit 33, whose functions are described in detail hereinbelow. Apparatus 20 is designed particularly for use in a motor vehicle (not shown in the figures) having a battery 32 and an engine 21, which rotationally drives alternator 22. A main relay 34 is used to close a circuit with battery 32 and start the engine, as is known in the art. It will be understood, however, that apparatus 20, with minor modifications, may similarly be used in conjunction with substantially any type of rotational drive input coupled to alternator 22.

Fig. 2A shows details of alternator 22 and associated circuitry, in accordance with a preferred embodiment of the present invention. Alternator 22 comprises two rotors 52 and 54, which may be arranged in parallel or in series, and are driven to rotate by engine 21. The rotors inductively drive two stators 56, denoted STATOR 1, comprising coils 53 and 57, and STATOR 2, comprising coils 55 and 59. By using dual rotors 52 and 54 and multiple stators 56, alternator 22 can be made more compact and efficient than alternators known in the art of comparable power output, or alternatively can be made to provide greater output power for a given overall size of the alternator.

STATOR 1 and STATOR 2 each have six output current phases. The outputs of coils 57 and 59 are coupled in parallel to a six-phase rectifier 25, which provides a DC output at terminals 23 to charge battery 32 (Fig. 1) or, alternatively, to provide welding power at 40-65 VDC and 350-400A. Rectifier 25 is preferably packaged as a part of alternator 22, as illustrated in Fig. 2A.

Alternatively, the outputs of coils 57 and 59 may be used to drive other high-power auxiliary equipment.

Switching of the output at terminals 23 between the battery and welding operation may be accomplished manually, simply by plugging and unplugging the appropriate leads. Alternatively, as shown in Fig. 1, a mode switch 42 may be operated by a user of apparatus 20 to switch between battery charging and welding by opening and closing a solenoid switch 40. A charging lamp 36 is lit under the control of circuit 33 (as described further hereinbelow with reference to Fig. 2D) to indicate that the output of alternator 22 is being used to weld or perform other operations, and not to charge battery 32.

Lamp 36 is extinguished when the alternator output is coupled to charge battery 32.

The outputs of coils 53 and 55 of STATOR 1 and STATOR 2 are respectively coupled to rectifiers 24, marked B3 and B2 respectively in Fig. 2A. For 220 VDC operation, the rectifier outputs are preferably coupled in parallel to one or more high-voltage receptacles 58.

Alternatively, the outputs may be coupled in series to provide a higher voltage output (in which case the value of resistor R63, shown in Fig. 2B, must be appropriately change. Preferably, apparatus 20 provides high-voltage output power of at least 6 kW. Additionally or alternatively, a supplementary power supply 43 may be coupled to the alternator output and used to provide another power output either AC or DC. Preferably, supply 43 outputs a DC voltage, for example, to charge a battery (and particularly to charge battery 32 while switch 40 is open). A center tap of each of coils 53 and 55 is grounded and connected to a ground terminal 49 of receptacle 58. The high-voltage output and ground are also coupled to monitor isometer 28, which cuts off the alternator output if a high-voltage ground fault is detected, and to regulator and fusing circuits 30, which cut off the output if an overload or short in the high- voltage output circuit is detected.

Fig. 2B is a schematic circuit diagram showing details of circuitry 26, and particularly of regulator control section of circuits 30, in accordance with a preferred embodiment of the present invention. One function of circuits 30 is to stabilize the 220 VDC output, independent of any load across the terminals of receptacle 58 and of the speed of rotation of alternator 22, by controlling the current input to rotors 52 and 54.

It will be appreciated, however, that with minor modifications, circuits 30 may also be coupled to a lower-voltage output of alternator 22, such as that provided at terminals 23, in order to provide a regulated output at 12,24 or 48 VDC, or at any other desired voltage.

The high-voltage input to circuits 30 is sampled by an opto-isolator 62, in order to maintain electrical isolation between the high-voltage circuits and battery 32, as well as between the high-voltage circuits and the low voltage and welding outputs and the body of the vehicle, with which the user may come in contact.

Resistors 61 divide the input voltage, such that when the voltage on a resistor 63 exceeds +2.5 V, a transistor 65 begins to conduct, and a current flows through a resistor 66 and through opto-isolator 62.

A controller 64 receives the output of opto-isolator 62 and outputs a pulse-width modulated (PWM) control signal to a gate 67. Controller 64 preferably outputs about 800 pulses per second, with a pulse width varying between 0 and 97% duty cycle. When gate 67 is switched on bv the PWM pulse, an input current flows from a 42 VDC or battery output via one of diodes 68 through the gate.

(The welding cables are connected directly to terminals 23, and no additional welding apparatus is needed.) The 42 VDC output is isolated from battery 32 by diodes 68.

When gate 67 is closed, rotor current can flow through a diode 69 and is therefore greatly increased. A comparator 71 is used to maintain the output of alternator 22 at its proper level when switch 40 is closed, and battery 32 is charging.

Fig. 2C is a schematic circuit diagram illustrating further aspects of circuits 30, in accordance with a preferred embodiment of the present invention. As this figure illustrates, these circuits sample the current in stator coils 53 and/or 55 and control the PWM output of controller 64 to cut off alternator 22 when an overload or short circuit is detected in the high voltage circuit.

Circuits 30 include a toroidal transformer 70, which is coupled to coil 53 of alternator 22 and generates a voltage proportional to the output current. A similar transformer and accompanying circuit (not shown) are preferably coupled to coil 55, as well, so that both STATOR 1 and STATOR 2 are monitored. When the voltage rises above a predetermined level, indicative of a possible short-circuit or overload in the alternator output, a reset signal is provided to the input of <BR> <BR> <BR> controller 64, which then interrupts the PWM output to gate 67. Once the overload or short-circuit is relieved, the controller resumes normal operation after a predetermined shut-off period, preferably about 3 sec.

Alternatively, an optional switch 74 may be used to provide the reset.

Circuits 30 also sample the rotor current using one or two resistors 60 coupled to gate 67 (Fig. 2B), which convert the current to a voltage in the range 0-0.5 V.

Typically only one resistor 60 is used when rotors 52 and 54 are connected in series (or equivalently if only a single rotor is used) whereas two resistors are used in the parallel rotor configuration, as illustrated in Fig.

2A. When the voltage input to circuits 30 from resistor (s) 60 exceeds a predetermined threshold, controller 64 receives an input which causes it to reduce <BR> <BR> <BR> the PrSM duty cycle accordingly. A potentiometer 72 may optionally be used to control the threshold level.

Fig. 2D is a schematic circuit diagram showing lamp driver circuit 33, in accordance with a preferred embodiment of the present invention. Circuit 33 receives a driving voltage W from coil 59 of alternator 22 (Fig.

2A). Typically W is approximately 9.5 VAC when battery 32 is charging, so that lamp 36 does not light. When terminals 23 are used for welding or other auxiliary activity, however, voltage W rises to about 17 VAC, causing lamp 36 to light and alert the user to the situation.

Apparatus 20 thus provides a more versatile, powerful and safer alternator/generator for vehicular use than alternators known in the art, by virtue of using dual rotors and multiple stator coils, and by using active control to maintain the output current and voltage within predetermined limits. Furthermore, because the 42 VDC output derived from coils 57 and 59 is self-holding, the generator output has a better dynamic response and gives higher power for a given engine speed than do welders known in the art.

Although in the preferred embodiment described above, apparatus 20 puts out certain specific DC voltage levels, it will be appreciated that the apparatus may be easily modified to provide a wide range of different voltages and currents. Moreover, although in the preferred embodiment, alternator 22 includes dual rotors 52 and 54 and dual stators 56, it will be appreciated that many of the inventive features of the present invention may similarly be used in alternators having only one rotor and/or stator, or having greater numbers of rotors and/or stators. It will thus be understood that the preferred embodiments described above are cited by way of example, and the full scope of the invention is limited only by the claims.